Matthew First up I applied some pale yellow oil paint to fade the existing colour. I added the pale yellow unevenly though, and especially on horizontal surfaces. Then for rust I used a small, ragged brush. I ran the side of the brush along the edges, and I used its ragged tip to randomly add the other rust patches and streaks. Paint was oil burnt sienna. The oil paint keeps its bulk better than acrylics and it helped to give the impression of blistering.
